scholarly journals CCD Photometry in the Globular Cluster M4

1995 ◽  
Vol 164 ◽  
pp. 411-411
Author(s):  
W.K. Griffiths ◽  
I.N. Kanatas ◽  
R.J. Dickens ◽  
A.J. Penny
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
Ccd Photometry ◽  
Magnitude Diagram ◽  
Red Giant

A V, B- V composite colour-magnitude diagram, based upon CCD photometry from V~ 12 on the red giant branch to V~ 25 on the main-sequence has been derived for the globular cluster M4. A distance to the cluster of (m – M)v = 12.84 ± 0.19 is determined and the best match to theoretical isochrones is for the case [Fe/H]=−1.27 and an age of 16±1 Gyr. A differential age comparison with NGC 362 shows that M4 is approximately 1.7 Gyr older.

scholarly journals UBVI CCD Photometry of an old Open Cluster AM-2

1996 ◽  
Vol 169 ◽  
pp. 435-436 ◽  
Author(s):  
Myung Gyoon Lee
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
Open Cluster ◽  
Ultraviolet Excess ◽  
Galactic Latitude ◽  
Ccd Photometry ◽  
Fitting Method ◽  
Age Ratio ◽  
Red Giant Clump ◽  
Red Giant

AM-2 is a sparse cluster located at low galactic latitude. It has been suspected to be a globular cluster. We present a study of AM-2 based on the deep UBVI CCD photometry obtained using the Las Campanas duPont 2.5m telescope. The color-magnitude diagrams of AM-2 show (a) a main-sequence extending up to V ≈ 19 mag at (B – V) ≈ 1.1 mag, (b) a small number of red giant clump giants, (c) the brightest red giant at V ≈ 16.1 mag and (B – V) ≈ 1.9 mag, and (d) a small group of mysterious blue stars at V ≈ 16.6 mag and (B – V) ≈ 0.9 mag. We have estimated the reddening using the color-color diagram, E(B – V) = 0.56 ± 0.04. The metallicity of the main-sequence stars has been estimated from the ultraviolet excess, δ(U – B)0.6 = 0.09 ± 0.04, to be [Fe/H] = −0.4 ± 0.2 dex. The distance to the cluster has been measured using the Zero-Age-Main-Sequence fitting method, (m – M)0 = 14.8 ± 0.3 (d = 9.1 ± 1.4 kpc). Finally we have estimated the age of the cluster using the Revised Yale isochrones and the Morphological Age Ratio (MAR) method, obtaining a value of 5 ± 1 Gyrs (Fig. 1). This shows that AM-2 is not a globular cluster, but an old open cluster.

scholarly journals Deep CCD Photometry in M 5

1988 ◽  
Vol 126 ◽  
pp. 623-623
Author(s):  
Harvey B. Richer ◽  
Gregory G. Fahlman
Keyword(s):  
Excellent Agreement ◽  
Globular Cluster ◽  
Main Sequence ◽  
Ccd Photometry ◽  
Upper Limit ◽  
Luminosity Functions ◽  
Magnitude Diagram ◽  
Metal Abundance ◽  
Mass Segregation

Deep UBV CCD imagery has been obtained in three fields of the galactic globular cluster M5. The locations of these fields are at distances of 8, 21, and 58 core radii. In the middle field, which overlaps substantially with the deep photometry field of Arp, the CCD photometry reaches fainter than V = 26. Color-magnitude diagrams constructed from stars in the inner two fields are identical, to within the errors, and can be used to set an upper limit of 4% to any metallicity difference between these two fields. A U, (U - V) color-magnitude diagram is also shown for the inner field and compared with that of a more metal rich and more metal poor cluster. Major differences in the morphology of these three diagrams are present as a function of metal abundance. From the color-color diagram the reddening in the direction of M5 is determined (E(B - V) = 0.02) as well as its metallicity ([M/H] = −1.13). The distance to M5 is then established from fitting local subdwarfs to the lower main sequence of the cluster. This yields (m - M)V = 14.3. Using the observationally determined parameters, an overlay of the appropriate VandenBerg and Bell isochrones yields an age estimate of 18 Gyrs for M5. Luminosity functions constructed from the three fields show excellent agreement through the range V = 17 to 23. Fainter than V = 23 there is some evidence for mass segregation effects due to dynamical relaxation.

scholarly journals Are Galactic globular cluster AGB stars rich or poor in Sodium? Sodium abundance of AGB and RGB stars in NGC 2808

2015 ◽  
Vol 12 (S316) ◽  
pp. 361-362
Author(s):  
Yue Wang ◽  
Francesca Primas ◽  
Corinne Charbonnel ◽  
Mathieu Van der Swaelmen ◽  
William Chantereau ◽  
...  
Keyword(s):  
Spectroscopic Study ◽  
Globular Cluster ◽  
Main Sequence ◽  
Significant Fraction ◽  
Agb Stars ◽  
2Nd Generation ◽  
Red Giant ◽  
Sodium Abundance

AbstractA spectroscopic study comparing the [Na/Fe] distributions of RGB and AGB stars in the Galactic globular cluster (GC) NGC 6752 found that there was no Na-rich, 2nd-generation star along the early-AGB of this cluster. This came as a surprise since in this GC, as well as other Galactic GCs studied so far, 1st- and 2nd-generation stars have usually been found from the main sequence turnoff up to the red giant branch. To investigate whether the failure of a significant fraction of stars to ascend the AGB also happens to other GCs, we studied a sample of AGB and RGB stars in NGC 2808 observed at the ESO/VLT with FLAMES. Contrary to NGC 6752, we find that the AGB and RGB stars we studied in NGC 2808 have comparable [Na/Fe] dispersions.

A Deep Luminosity Function for 47 Tucanae

1985 ◽  
Vol 113 ◽  
pp. 81-83
Author(s):  
William E. Harris ◽  
James E. Hesser
Keyword(s):  
Luminosity Function ◽  
Main Sequence ◽  
Ccd Photometry ◽  
Magnitude Diagram

CCD photometry in B and V reaching B(lim) ≃ 25 has been employed to obtain the luminosity function and color-magnitude diagram for the main sequence of 47 Tuc. For 5<Mv<10 we find that its LF is essentially flat (Δlog n/Δm~0). The CMD is successfully matched by isochrones with [Fe/H] = −0.5 and t ≃ 15 × 109y.

scholarly journals Globular cluster candidates in the Galactic bulge: Gaia and VVV view of the latest discoveries

2019 ◽  
Vol 628 ◽  
pp. A45 ◽  
Author(s):  
F. Gran ◽  
M. Zoccali ◽  
R. Contreras Ramos ◽  
E. Valenti ◽  
A. Rojas-Arriagada ◽  
...  
Keyword(s):  
Main Sequence ◽  
Star Clusters ◽  
Forthcoming Paper ◽  
Variable Stars ◽  
Star Cluster ◽  
Proper Motions ◽  
Magnitude Diagram ◽  
Spatial Coordinates ◽  
Red Giant ◽  
Moving Groups

Context. Thanks to the recent wide-area photometric surveys, the number of star cluster candidates have risen exponentially in the last few years. Most detections, however, are based only on the presence of an overdensity of stars in a given region or an overdensity of variable stars, regardless of their distance. As candidates, their detection has not been dynamically confirmed. Therefore, it is currently unknown how many and which of the published candidates are true clusters and which are chance alignments. Aims. We present a method to detect and confirm star clusters based on the spatial distribution, coherence in motion, and appearance on the color-magnitude diagram. We explain and apply this approach to one new star cluster and several candidate star clusters published in the literature. Methods. The presented method is based on data from the second data release of Gaia complemented with data from the VISTA Variables in the Vía Láctea survey for the innermost bulge regions. This method consists of a nearest neighbors algorithm applied simultaneously over spatial coordinates, star color, and proper motions to detect groups of stars that are close in the sky, move coherently, and define narrow sequences in the color-magnitude diagram, such as a young main sequence or a red giant branch. Results. When tested in the bulge area (−10 <  ℓ (deg) <  +10; −10 <  b (deg) <  +10) the method successfully recovered several known young and old star clusters. We report in this work the detection of one new, likely old star cluster, while deferring the others to a forthcoming paper. Additionally, the code has been applied to the position of 93 candidate star clusters published in the literature. As a result, only two of these clusters are confirmed as coherently moving groups of stars at their nominal positions.

scholarly journals The Abundance of the LMC Globular Cluster NGC 2213

1988 ◽  
Vol 126 ◽  
pp. 579-580
Author(s):  
Doug Geisler
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
High Accuracy ◽  
Magellanic Cloud ◽  
New Technique ◽  
Distance Modulus ◽  
Ccd Photometry ◽  
Cloud Clusters ◽  
A New Technique ◽  
Using Data

A new technique for determining accurate abundances in distant giants - Washington CCD photometry - has been applied to the intermediate-age LMC globular cluster NGC 2213. An abundance of −0.40 ± 0.15 was found from the analysis of 42 giants with V < 20, using data obtained with the 1.5 m telescope. Combined with published main-sequence photometry, the derived abundance indicates a true LMC distance modulus of 18.2 ± 0.2. A likely CN strong giant near the tip of the giant branch is identified. Abundances are also derived for a sample of 27 field giants. Results indicate that one could determine both the age and abundance of Magellanic Cloud clusters with high accuracy from Washington photometry using the 4 m in less than one hour of observing time per cluster.

scholarly journals The Influence of Rotation on Horizontal Branch Stars and on RR Lyrae Pulsational Properties

1981 ◽  
Vol 93 ◽  
pp. 275-275
Author(s):  
V. Castellani
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
Horizontal Branch ◽  
Structural Variations ◽  
Rr Lyrae ◽  
Horizontal Branch Stars ◽  
Mass Size ◽  
Red Giant

The occurrence of rotation in Globular Cluster stars has been suggested (see e.g. Renzini 1977) as a mechanism producing the observed colour spread in actual Horizontal Branches. If this is the case, canonical results on evolutionary properties of HB stars have to be revisited in order to account for rotation-driven structural variations: faster Main Sequence rotators delay the He flash increasing the mass-size Mc of the He core at the flash and loosing a greater amount of mass during the Red Giant stage.

scholarly journals Pal 1: A Globular Cluster Anyway?

1995 ◽  
Vol 164 ◽  
pp. 395-395
Author(s):  
J. Borissova ◽  
N. Spassova
Keyword(s):  
Globular Cluster ◽  
Luminosity Function ◽  
Main Sequence ◽  
Structural Parameters ◽  
Distance Modulus ◽  
Horizontal Branch ◽  
Ccd Photometry ◽  
Horizontal Branch Stars ◽  
Mass Estimate

CCD photometry of the halo cluster Pall in Thuan-Gunn system is presented. The color - magnitude diagrams (Fig. 1) show a well defined red horizontal branch, lower giant branch and main-sequence down to about two magnitudes below the main-sequence turnoff. The giant branch is absent and the brightest stars are horizontal-branch stars. The horizontal branch is composed of red stars only. The age of the cluster, determined by comparison with the isochrones of Bell and Vanden Berg (1987) is consistent with an age between 12 – 14 Gyr. and a metallicity [Fe/H] = −0.79. The observed luminosity function shows a deficiency of stars from about 0.5 mag below turnoff up to g = 21 mag. A distance modulus of (m – M)g0 = 15.35 ± 0.1 magnitude has been derived. An estimate of the cluster structural parameters gives rc = 1.7 pc and c = 1.46. A mass estimate of 1.6 × 103M⊙ and mass-to-light ratio 1.77 has been obtained, using King's (1966) method.

Wide Field Multicolor CCD Photometry of the Open Cluster NGC752

2010 ◽  
Vol 19 (1-2) ◽  
Author(s):  
J. Zdanavičius ◽  
S. Bartašiutė ◽  
K. Zdanavičius
Keyword(s):  
Main Sequence ◽  
Open Cluster ◽  
Wide Field ◽  
Ccd Photometry ◽  
Magnitude Diagram

AbstractThe results of CCD photometry in the seven-color Vilnius system of 3058 stars down to V ~ 18.0 mag in a 1.5 square degree field around the cluster NGC 752 are presented. For most of the stars brighter than V = 17.0 mag, photometric spectral and luminosity classes are determined. The catalog of 1174 stars down to V = 15.5 mag is given in the paper. The entire catalog will be available at the CDS Simbad database. The color-magnitude diagram indicates an extension of the cluster’s main sequence down to 5 mag below the turnoff point.

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